The present invention relates generally to a device for cutting both hard and soft materials and, more particularly, to a device for combining electromagnetic and hydro energies for cutting and removing both hard and soft tissues.
Turning to FIG. 1, a prior art optical cutter for dental use is disclosed. According to this prior art apparatus, a fiber guide tube 5, a water line 7, an air line 9, and an air knife line 11 (which supplies pressurized air) are fed into the hand-held apparatus 13. A cap 15 fits onto the hand-held apparatus 13 and is secured via threads 17. The fiber guide tube 5 abuts within a cylindrical metal piece 19. Another cylindrical metal piece 21 is a part of the cap 15.
When the cap 15 is threaded onto the hand-held device 13, the two cylindrical metal tubes 19 and 21 are moved into very close proximity of one another. A gap of air, however, remains between these two cylindrical metal tubes 19 and 21. Thus, the laser within the fiber guide tube 5 must jump this air gap before it can travel and exit through another fiber guide tube 23. Heat is dissipated as the laser jumps this air gap.
The pressurized air from the air knife line 11 surrounds and cools the laser as the laser bridges the gap between the two metal cylindrical objects 19 and 21. Thus, a first problem in this prior art apparatus is that the interface between the two metal cylindrical objects 19 and 21 has a dissipation of heat which must be cooled by pressurized air from the air knife line 11. (Air from the air knife line 11 flows out of the two exhausts 25 and 27 after cooling the interface between elements 19 and 21.) This inefficient interface between elements 19 and 21 results from the removability of the cap 15, since a perfect interface between elements 19 and 21 is not achieved.
The laser energy exits from the fiber guide tube 23 and is applied to a target surface within the patient's mouth, according to a predetermined surgical plan. Water from the water line 7 and pressurized air from the air line 9 are forced into the mixing chamber 29. The air and water mixture is very turbulent in the mixing chamber 29, and exits this chamber through a mesh screen with small holes 31. The air and water mixture travels along the outside of the fiber guide tube 23, and then leaves the tube and contacts the area of surgery. This air and water spray coming from the tip of the fiber guide tube 23 helps to cool the target surface being cut and to remove cut materials by the laser. The need for cooling the patient surgical area being cut is another problem with the prior art.
In addition to prior art systems which utilize laser light from a fiber guide tube 23, for example, to cut tissue and use water to cool this cut tissue, other prior art systems have been proposed. U.S. Pat. No. 5,199,870 to Steiner et al., which issued on Apr. 6, 1993, discloses an optical cutting system which utilizes the expansion of water to destroy and remove tooth material. This prior art approach requires a film of liquid having a thickness of between 10 and 200 mm. Another prior art system is disclosed in U.S. Pat. No. 5,267,856 to Wolbarsht et al., which issued on Dec. 7, 1993. This cutting apparatus is similar to the Steiner et al. patent, since it relies on the absorption of laser radiation into water to thereby achieve cutting.
Similarly to the Steiner et al. patent, the Wolbarsht et al. patent requires water to be deposited onto the tooth before laser light is irradiated thereon. Specifically, the Wolbarsht et al. patent requires water to be inserted into pores of the material to be cut. Since many materials, such as tooth enamel, are not very porous, and since a high level of difficulty is associated with inserting water into the "pores" of many materials, this cutting method is somewhat less than optimal. Even the Steiner et al. patent has met with limited success, since the precision and accuracy of the cut is highly dependent upon the precision and accuracy of the water film on the material to be cut. In many cases, a controllable water film cannot be consistently maintained on the surface to be cut. For example, when the targeted tissue to be cut resides on the upper pallet, a controllable water film cannot be maintained.
The above-mentioned prior art systems have all sought in vain to obtain "cleanness" of cutting. In several dental applications, for example, a need to excise small amounts of soft tissues and/or hard tissues with a great degree of precision has existed. These soft tissues may include gingiva, frenum, and lesions and, additionally, the hard tissues may include dentin, enamel, bone, and cartilage. The term "cleanness" of cutting refers to extremely fine, smooth incisions which provide ideal bonding surfaces for various biomaterials. Such biomaterials include cements, glass ionomers and other composites used in dentistry or other sciences to fill holes in structures such as teeth or bone where tooth decay or some other defect has been removed. Even when an extremely fine incision has been achieved, the incision is often covered with a rough surface instead of the desired smooth surface required for ideal bonding.
One specific dental application, for example, which requires smooth and accurate cutting through both hard and soft tissues is implantology. According to the dental specialty of implantology, a dental implant can be installed in a person's mouth when that person has lost his or her teeth. The conventional implant installation technique is to cut through the soft tissue above the bone where the tooth is missing, and then to drill a hole into the bone. The hole in the bone is then threaded with a low-speed motorized tap, and a titanium implant is then screwed into the person's jaw. A synthetic tooth, for example, can be easily attached to the portion of the implant residing above the gum surface. One problem associated with the conventional technique occurs when the clinician drills into the patient's jaw to prepare the site for the implant. This drilling procedure generates a great deal of heat, corresponding to friction from the drilling instrument. If the bone is heated too much, it will die. Additionally, since the drilling instrument is not very precise, severe trauma to the jaw occurs after the drilling operation. The drilling operation creates large mechanical internal stress on the bone structure.